The present invention relates generally to harvesting machines, commonly referred to as combine harvesters and, more particularly, is directed to combine harvesters built according to a modular concept.
In known combine harvesters, grain is threshed and separated in a threshing and separating mechanism and the separated grain, together with the impurities, such as chaff, dust, straw particles, and tailings, is fed to a cleaning mechanism for cleaning. Clean grain is collected below the cleaning mechanism and fed to a grain tank for temporary storage. The tailings are separated from the clean grain and impurities for reprocessing. This reprocessing either involves recycling the tailings through the threshing and separating mechanism or treating them in a separate tailings rethreshing means.
In the standard commercially available combines, the rotatable threshing cylinder and cooperable concave extend transversely to the direction of movement of the combine. The crop is fed to the concave and passed between the concave and threshing cylinder whereby it is threshed. The straw is discharged rearwardly of the concave onto reciprocating or oscillating straw walkers that extend longitudinally of the combine. Much of the grain contained in the crop material fed to the threshing mechanism is threshed and separated by that mechanism and some of the remainder is separated from the straw while the latter is on the straw walkers. Straw walkers have proved to be the capacity limiting components of the standard combine because, when operating at high capacity rates, much grain is discharged with the straw to the straw walkers which are unable to cope with the required separation, and hence unacceptable grain losses occur
Recent developments in combine harvesters have led to so-called rotary machines wherein both threshing and separating are accomplished in mechanisms comprising rotary components cooperable with respective stationary threshing and separating concaves and grates. In rotary combines the crop material is subjected to a much more aggressive and positive separating action during a relatively prolonged period of time, whereby the efficiency of a rotary combine harvester usually is greater than that of a conventional machine.
Several different types of rotary combine harvester have appeared on the market and in one such machine a conventional transversely-extending, threshing mechanism having a threshing cylinder and a cooperable concave is combined with a rotary separating mechanism having a rotor of a width greater than that of the threshing mechanism and disposed parallel thereto with its end extending transversely past the respective ends of the threshing mechanism. The rotary separating mechanism operates spirally to convey the crop material received from the threshing mechanism towards each of its end, while submitting the crop to a separating action. With such a separating mechanism, the incoming layer of crop material has to be divided in two substantially equal portions, each of which is then spirally conveyed from the center of the separating mechanism to one or other of its ends.
In another type of rotary combine, commonly referred to as an axial flow combine harvester, the threshing and separating mechanism extends longitudinally (fore-and-aft) of the machine, parallel to the direction of movement and comprises at least one threshing and separating rotor and cooperable concave. The crop material is fed to the forward end of the threshing mechanism and is formed into a mat which passes generally axially therethrough in a spiral path. In axial flow machines, the crop material is subjected to a threshing and separating action far longer than in a standard machine of comparable size and, therefore, the efficiency of the former is greater than the efficiency of the latter.
It has been proven in practice that the conventional combines and the rotary combines both have advantages and disadvantages which influence the end user's buying decision. Accordingly, there is a market for both conventional and rotary combines.
Turning now to the cleaning apparatus of both conventional and rotary combines, it is readily appreciated that the efficiency of a cleaning system of a combine harvester is greater if threshed crop material is fed thereto in a regular manner and the cleaning air blast is uninterrupted. As a rule, this is achieved only if the combine harvester is in a virtually horizontal position. When the ground is irregular, and particularly when inclined, different things can happen in the cleaning mechanism dependent on a number of factors, such as the direction and extent of the inclination of the combine to the horizontal. When the combine harvester is oriented such that it is inclined to the horizontal transversely in relation to the direction of travel, crop material separated from the straw in the threshing and separating means tends to move to the lower side of the grain pan. This sideward shifting of crop material is continued during its transport along the grain pan, during its transfer from the grain pan to the cleaning sieves, during its movement across the cleaning sieves and during its fall from one sieve to another sieve disposed therebelow. The result of all this is that the higher sides of the sieves are virtually free of crop material while the lower sides thereof are so heavily loaded with crop material that clogging may occur. This, in turn, results in grain emerging from the combine harvester at the rear instead of passing through the sieves and causing considerable grain losses at the lower side of the sieves. With uneven loading of the sieves, the cleaning air blast is unequally effective, so that cleaning is diminished considerably. Indeed, cleaning air tends to escape through the underloaded sieve sections, thus leaving the overloaded sieve sections with a reduced air blast.
One solution to this problem has been given by the provision of an automatically self-leveling cleaning apparatus such as disclosed in Great Britain Pat. No. 2,052,238. Other solutions equally are available on the market. It will be appreciated that farmers will want such a self-leveling cleaning apparatus only when they have to operate their combine in hilly conditions. Otherwise, the additional cost for such an apparatus is not warranted.
All the foregoing means that, to be able to meet all customer requirements, a manufacturer would have to offer a very wide range of combine models, which is economically undesirable, especially in times when the market for combine harvesters is in a downturn and pressure on prices is high.